The protesters are affiliated with the English Defense League (EDL), a political movement that opposes Islamic immigration to the United kingdom.

The protesters have traveled to Woolwich, the scene of attack. Reporters tweeting from the scene describe a crowd of 100 or so, chanting and throwing projectiles at police officers. Many of the crowd are wearing masks:

More EDL. Some now in balaclavas: twitter.com/AliBunkallSKY/…— Alistair Bunkall (@AliBunkallSKY) May 22, 2013

At least 100 people now chanting Rule Britannia in Woolwich's main square twitter.com/NicoHines/stat…— Nico Hines (@NicoHines) May 22, 2013

Members of the EDL had taken to the group's Twitter and Facebook accounts today, calling on people from all around the country to travel to Woolwich and (in their words) "tell the religion of peace we don't want them here."